Study On Aqueous Extract From Galla Chinensis As An Root Canal Disinfectant Against Enterococcus Faecalis

Enterococcus faecalis ,formerly classified as part of the Group D Streptococcus system , is a Gram-positive commensal bacterium inhabiting the gastrointestinal tracts of humans and other mammals, causes up to 90% of enterococcal infections in humans and now rank among the top three nosocomial bacterial pathogens.Enterococci have also been implicated in endodontic failures,it was rarely found in infected but untreated root canals and was among a group of bacteria cultured from periapical lesions refractory to endodontic treatment. It has the ability to invade dentinal tubules easily and is resistant to most of the intracanal medicaments, particularly to calcium hydroxide dressings .It can withstand harsh environmental conditions and survive prolonged starvation, furthermore, it can grow as a mono-infection in treated canals in the absence of synergistic support from other bacteria .E. faecalis can remain in the dentinal tubules after instrumentation and antibacterial irrigation and cause such problems such as treatment failure .An antimicrobial dressing is nessasary to eliminate the residual microorganisms .The clinical commonly used disinfectants either perform poorly or have obvious side toxic effects. For improving the therapeutic effects of root canal therapy we need to find a effective and safe disinfectant against E. faecalis.Gallotannins represent the major constituent (>90%) of Galla chinensis and have been reported to have strong antibacterial activities.Former studies proved that the aqueous extract of Galla chinensis possesses broad spectrum antibacterial activities on anaerobic strains from the infected root canals, its water decoction can efficiently kill the drug resistant strains isolated from nosocomial infection patients in vitro. Furthermore, as a natural medicine, Galla chinensis is not inclined to develop drug resistance and has less side effects, which suggest that it could be developed into an ideal root canal disinfectant.The aim of this study is to explore the possibility of Galla chinensis used as a root canal disinfectant against E. faecalis, its antibacterial efficacy on E. faecalis under different status: planktonic bacteria, bacteria in root canal tubules and bacteria of single biofilm were detected. Its effect on adherence ability of E faecalist o collagen and micro-hardness of root canal wall were evaluated.1. In vitro study of the antibacterial activities of the aqueous extract of Galla chinensis on E. faecalis.The minimal inhibitory and bactericidal concentrations (MIC and MBC) were assayed by using a broth dilution technique in vitro.Chlorhexidine and tannic acid were used as controls. The aqueous extract of Galla chinensis showed satisfactory antibacterial activity against E. faecalis, it behaved germicidal effect on the concentration of 6.25mg/mL.2. In vitro study on the efficacy of the aqueous extract of Galla chinensis in sterilizing E. faecalis infected bovine dentin tubules. An in vitro model for bovine dentinal tubule infection of root canals was developed. The disinfecting efficacy of 200mg/mL Galla chinensis against E. faecalis-infected dentin was evaluated. 2% Chlorhexidine was used as positive control. The results showed that 200mg/mL Galla chinensis need a little longer action time to disfect the dentin than 2% Chlorhexidine does.However, there was no viable organism can be detected when the treatment maintained for 1d or longer in both groups.3. In vitro study on the effect of Galla chinensis on the vitality of E faecalis in mono-biofilm.After being stained by fluorescent probes, the effect of Galla chinensis on the vitality of E faecalis in the mono-biofilm formed on glass slides for 24h was observed by confocal laser scanning microscopy. Chlorhexidine was used as positive control.The results showed that Galla chinensis decreased the vitality of E faecalis in the biofilm significantly, and the proportion of dead bacteria increased with the elongation of treatment time. After being treated for 30 minutes, most of the bacteria in the film were killed.Furthmore, bacteria colony seemed to be more dispersed in Galla chinensis group.4. In vitro study on the effect of the aqueous extract of Galla chinensis on adhesion ability of E. faecalis .This study comprised two parts: first, the effect of Galla chinensis on adhesion ability of E. faecalis to SigmaScreen? Collagen I coated plates was evaluated, and then the effect of Galla chinensis on adhesion ability of E. faecalis to dentin was observed on the scanning electron microscope by using an in vitro model for bovine dentinal tubule infection of root canals. The results showed that the pretreatment of Galla chinensis significantly inhibited the adherence of E. faecalis to collagen or dentin. 5. The effect of the aqueous extract of Galla chinensis on micro-hardness of root canal wallsAfter the smear layers were removed, the bovine dentin blocks were split longitudinally into halves and treated by 200mg/mL Galla chinensis.Then the micro Vickers hardness of the blocks were examined.17% EDTA was used as a control. The result showed that the micro-hardness of root canal walls wasn't reduced significantly after being treated with Galla chinensis for 1day or 7days, while the micro-hardness was declined markedly after being treated with EDTA for 10mins.